The present invention relates generally to installation of underground cables and, more particularly, to methods and apparatus for installing underground electrical cables to a padmount transformer.
Previously, primary and secondary electrical cables have been buried by constructing a trench with a backhoe. These cables were preferably to be closely aligned with each other and the transformer bushings so that elbows and terminations could be installed as easily as possible. To ensure this correct placement, previous installations relied upon the presence of one or two people actually within the trench and holding the cables in place while the trench was being backfilled.
In addition to requiring more time and labor than desired, such methods have proven to be dangerous for those persons in the trench. As a result of the depth of the trench, the equipment used in backfilling and the environmental conditions of the job site, serious accidents were not uncommon from trench cave ins.
To overcome those disadvantages, the applicant has experimented with use of mechanical templates which hold and align the cables, instead of people, during the backfill process. However, in developing such devices it has become apparent that certain practical, and often conflicting, criterion exist. Ideally, the template must be large enough to span the trench width with sufficient clearance to remain stable during backfilling. However, the template should not be too heavy or bulky for a single person to lift, carry and place, or else the manpower savings is not sufficiently reduced. On the other hand, since backfilling operations can be delayed unexpectedly and job site environments are often muddy, the template must be sufficiently rugged to remain in place without deterioration. Further, its dimension should not preclude backfilling under the template itself. In addition, the cable attachment must be secure, but not too cumbersome to apply and remove. Naturally, the entire construction should ideally be inexpensive and easy to fabricate.
To achieve these and other objectives, the applicant has provided a template having an expandable base with a plurality of raised side cavities to receive and retain underground cables prior to, during and after trench backfilling. The base includes slidable wings to assist in bridging the trench and stabilizing the base on adjacent ground. A back member is removably attached to the base to bridge the cavities and secure the cables therein. A guide is provided for receiving a grounding rod, and a central opening is formed in the base as a hand hold and to permit backfilling under the base if needed. The entire assembly is preferably constructed from aluminum.
In use, the base is positioned over the trench at the desired location for the padmount transformer, and the wings are extended over the adjacent ground. The cables are preferably placed in conduit sleeves and then secured within the cavities. The base is securely grounded, and then the trench is backfilled. After backfilling is finished the back member is released from the base, and the base is separated from the cables. The cables, preferably still in the conduit sleeves, are then attached to the padmount transformer.
Other objects, advantages and novel features of the present invention will now become readily apparent to those skilled in the art upon consideration of the drawings and detailed description below.